The present invention relates to extended unattended video recording and to remote control devices. The invention addresses the need to monitor a location or process unattended for an extended period of timexe2x80x94typically much greater than the time capacity of a standard recording tape.
One technique for efficient extended recording is time lapse recording. Time lapse recording enables reproduction in less than the actual time period. For example, in reproducing a weather radar picture occurring over an extended period, say twenty-four hours, the recorder is operative to record the radar screen only at spaced time intervals; and, the recordings or takes are successive on the recorded tape for playback in continuous sequence. By way of example, if a videotape recorder were actuated to record every five minutes for a period of five seconds then there would be recorded one minute for each hour. In this example, there is a time compression of 60 to 1. Of course, these rates and periods may be selected, as desired.
There are prior art devices for extended recording. The most well known of these that use time-lapse recording techniques are time lapse videocassette recorders. These are highly specialized, expensive devices. They do not have an integrated video camera and most often must be permanently installed at the location to be monitored.
Scott U.S. Pat. No. 4,271,437 recognizes the advantages of adapting a more standard video-recording device to be used as a time lapse video recorder. Even the Scott device however requires a more specialized videocassette recorder than those most commonly used. It requires that the videocassette recorder it interfaces with have separate electrical inputs for play, rewind, and edit commands. Because the Scott device uses an electrical interface, it cannot be used with camcorders, which use an infrared interface. Also, because timing is set with physical components such as capacitors, the Scott device does not allow for easy changing of the time lapse parameters such as the period between video samples and the length of each sample. In addition, the Scott device requires that the recording tape be pre-recorded with control signals.
Another device commercially available uses a recording time extension method different than time-lapse recording. This device receives signals from a motion detector. When motion is detected, the device sends a record command to a video cassette recorder through an infrared signal. A period of time after the motion signal is detected, the device sends an infrared command to stop recording. In this way, the video cassette recorder is recording only when there is activity of interestxe2x80x94presumably when people or animals are moving in the range of the motion detector. One obvious limitation of this device is that it is limited to recording events that can be detected by a motion detector. Among these limitations are:
The event must include a moving object.
The moving object must radiate heat.
The moving object must be close to the motion detector.
A window cannot separate the moving object and the motion detector. The glass will block the heat radiation given off by the moving object.
Also, the amount of time compression is set by the event being monitored and is therefore unpredictable. In other words, if the motion detector is constantly being triggered, the recording tape time will be consumed more quickly than if there is less motion.
There is much prior art regarding remote control devices. Most of the prior art is concerned with methods of controlling as many devices as possible with a single remote control. This includes efficient storage of a large number of command sets in the limited memory of a microprocessor and efficient recall of these command sets. Examples of this are: Wells II U.S. Pat. No. 4,623,887, Rumbolt et al U.S. Pat. No. 4,703,359, and Hayes et al U.S. Pat. No. 5,614,906. These devices are concerned with immediate user control of a consumer device such as a TV, videocassette recorders, or a cable TV converter box. These are not concerned with controlling devices unattended.
It is an important object of the present invention to provide a method and apparatus to allow for unattended video recording over extended periods of time using standard video recording devices. Several objects and advantages of the present invention are:
It is much less expensive.
It is much more self-contained and portable.
Recording parameters can be varied much easier.
It is not confined to events that can be detected by a motion detector.
The amount of extended recording time is predictable.
It takes advantage of new advances in recording technology that are generally incorporated into mass-produced consumer products first.
The benefits of the present invention become most apparent when used in conjunction with a camcorder and for the most part will be described for use with a camcorder. Other video recording devices such as videocassette recorders can also be used.
Personal video recording devices, commonly known as xe2x80x9ccancordersxe2x80x9d include within them high quality optics, precise electromechanical systems for auto-focusing, sensitive high resolution electro-optic sensors, and the means to store a large amount of video information on inexpensive magnetic tape. Most also have the capability of noting the time and date a recording was taken. Because of mass production, camcorders are quite inexpensive given the amount of technology that goes into them. The main problem with using a camcorder for extended unattended monitoring is the limited recording time of the recording tape (typically 2 hours). A practical device would have a capability of at least 24 hours.
To extend the recording time of a camcorder, a remote control is used to control the recording intervals of the camcorder. One of the most powerful recording time-extending techniques is time lapse recording. For time lapse recording, a remote control is used to periodically command the camcorder to record for relatively short periods of time and then stop recording. In other words, periodically take video samples. Most camcorders can be remotely controlled by infrared signals. The new extended time is given by the formula:
Text=Tnorm*[(Tstandby/Trecord)+1]xe2x80x83xe2x80x83Equation 1
Time Compression=Text/Tnorm=(Tstandby/Trecord)+1xe2x80x83xe2x80x83Equation 2
Where:
Text=The new extended time
Tnorm=The normal recording time
Trecord=The time the camcorder is recording during each video sample. In other words, the time lapse record interval.
Tstandby=The time the camcorder is not recording between each video sample. In other words, the time lapse standby interval.
In this way, a standard camcorder can be used to video monitor a location or process unattended for an extended period of timexe2x80x94typically much greater than the time capacity of a standard recording tape. The sample time and the time between samples would be adjusted depending on the nature of the event to be captured and the total monitoring time required. Another way to extend the recording time is to completely disable the recording during periods of time when an event of interest is known not to occur or cannot be recorded. For example, if there were no artificial lighting at all, it would not make sense to record at night.
Another way would be to combine the technique of using a sensor such as a motion detector to modify the time-lapse recording when a special event occurs.
In cases where there is no AC power available, battery energy can limit the recording time even more so than tape capacity. Although most camcorders can be remotely commanded to start and stop recording, they cannot be remotely commanded to turn themselves completely off. Even when not recording, and in a xe2x80x9cstand byxe2x80x9d mode, most camcorders draw significant power from their power source. In this case, an infrared controlled switch that is sensitive to commands from the remote control can be placed in series with the camcorder battery. This infrared controlled switch would switch power off and on from the battery to the camcorder based on commands from the remote control in the same way the tape recording is enabled and disabled. In this way the battery lifetime can be extended by the same techniques as the taping time is extended.